(which will be labeled as "Display Sleep Timer" (the value 0 is for Never—otherwise, it's straight numeric by minutes) or

pmset -g custom

(which will be labeled as displaysleep).

How do you change the settings?

To modify it for all power settings (according to the man page for pmset, there are separate parameters for a wall charger versus a UPS, so it's easier to modify for all and then just modify battery afterwards), you'd enter this command into the terminal:

sudo pmset -a displaysleep 180

(for three hours, as an example) and then enter this command into the terminal:

sudo pmset -b displaysleep 25

(for 25 minutes, as an example) to modify just the battery settings.

If you look at /Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist or the output of pmset -g custom, you'll see your changes take immediately. If, however, you look at Energy Saver through System Preferences, you'll see that the changes aren't reflected immediately without a logout or a reboot.